Aphidicolin is an antimitotic and antiviral mold metabolite produced by Cephalosporium aphidicola. It strongly inhibits the growth of herpes simplex virus both in tissue culture and in the rabbit eye, and does not induce formation of drug resistant strains. Structurally, aphidicolin belongs to a new skeletal type of diterpenes. We propose to synthesize aphidicolin with the hope that, once a general route is available, synthetic analogues with increased activity can be made. We have carried out a considerable amount of work and are now within reach of the goal.